1. Field of the Invention
The present invention relates to a device and method for enhancing the light trapping in light harvesting devices. Particularly, the present invention relates to collecting light from a large surface area of the light harvesting device comprising a light absorbing material and trapping the light within the device so as to increase the optical path through the light absorbing material and improve the useful light absorption. More particularly, the present invention relates to enhancing the light trapping in photovoltaic solar panels, light detectors, day lighting systems, bioreactors, water light-treatment reactors, and the like. The present invention also relates to illumination devices, particularly to light emitting panels and conduits.
2. Description of Background Art
Many light harvesting devices employ a light-absorbing active layer that has at least a partial transparency with respect to the incident light or absorbs more weakly in certain wavelengths than in the others. Conventionally, the absorption in such devices can be improved by increasing the thickness of the active layer. However, this results in the increased system dimensions, material consumption, weight and cost. Alternatively, light trapping approaches are well known in which the light path is altered within the device by micro-texturing one or more device surfaces. While this allows to somewhat increase the light path and thus improve absorption compared to a non-textured device, a significant portion of the light still escapes from the device without being fully absorbed. It is therefore an object of this invention to provide an improved optical structure that can be used in conjunction with light harvesting devices and that can provide efficient light trapping with minimal energy loss.
The present invention solves the above problems by providing a transparent optical cover structure having one or more micro-structured surfaces that allow for trapping the incident light within the light harvesting device by means of at least TIR and cause the multiple passage of the trapped light through the active layer thus improving the light absorbtion and device efficiency at the minimum consumption of active layer's material.
Many light emitting devices employing panel-like structures, such as lighting panels or backlights designed to distribute light along the surface of the panel and emit light from one or more broad surfaces of the panel, are limited to conducting light propagating at relatively high TIR angles with respect to a normal to the panel surface. Furthermore, many such light emitting devices employ light extracting features that impair the optical transparency of the device or/or involve additional fabrication steps or materials, such as selective surface metallization or using, adding reflectors which increases system complexity and cost.
The present invention solves these problems by providing a transparent optical cover structure having one or more micro-structured surfaces that allow for light propagation along the panel in a greater angular range and provide for an efficient light distribution and extraction mechanism.
Other objects and advantages of this invention will be apparent to those skilled in the art from the following disclosure.